/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.iceberg.orc;

import com.google.common.collect.Lists;
import org.apache.iceberg.types.Type;
import org.apache.iceberg.types.Types;
import org.apache.orc.TypeDescription;

import java.util.List;

public abstract class OrcSchemaWithTypeVisitor<T>
{
    public static <T> T visit(org.apache.iceberg.Schema iSchema, TypeDescription schema, OrcSchemaWithTypeVisitor<T> visitor)
    {
        return visit(iSchema.asStruct(), schema, visitor);
    }

    public static <T> T visit(Type iType, TypeDescription schema, OrcSchemaWithTypeVisitor<T> visitor)
    {
        switch (schema.getCategory()) {
            case STRUCT:
                return visitRecord(iType != null ? iType.asStructType() : null, schema, visitor);

            case UNION:
                throw new UnsupportedOperationException("Cannot handle " + schema);

            case LIST:
                Types.ListType list = iType != null ? iType.asListType() : null;
                return visitor.list(
                        list, schema,
                        visit(list != null ? list.elementType() : null, schema.getChildren().get(0), visitor));

            case MAP:
                Types.MapType map = iType != null ? iType.asMapType() : null;
                return visitor.map(
                        map, schema,
                        visit(map != null ? map.keyType() : null, schema.getChildren().get(0), visitor),
                        visit(map != null ? map.valueType() : null, schema.getChildren().get(1), visitor));

            default:
                return visitor.primitive(iType != null ? iType.asPrimitiveType() : null, schema);
        }
    }

    private static <T> T visitRecord(Types.StructType struct, TypeDescription record, OrcSchemaWithTypeVisitor<T> visitor)
    {
        List<TypeDescription> fields = record.getChildren();
        List<String> names = record.getFieldNames();
        List<T> results = Lists.newArrayListWithExpectedSize(fields.size());
        for (TypeDescription field : fields) {
            int fieldId = ORCSchemaUtil.fieldId(field);
            Types.NestedField iField = struct != null ? struct.field(fieldId) : null;
            results.add(visit(iField != null ? iField.type() : null, field, visitor));
        }
        return visitor.record(struct, record, names, results);
    }

    public T record(Types.StructType iStruct, TypeDescription record, List<String> names, List<T> fields)
    {
        return null;
    }

    public T list(Types.ListType iList, TypeDescription array, T element)
    {
        return null;
    }

    public T map(Types.MapType iMap, TypeDescription map, T key, T value)
    {
        return null;
    }

    public T primitive(Type.PrimitiveType iPrimitive, TypeDescription primitive)
    {
        return null;
    }
}
